1. Field of the Invention
The present invention relates to a reactor process and apparatus to treat extra heavy crude petroleum containing high concentrations of asphaltenes, acids, metals and heteroatoms. In particular, the present invention is directed to a reactor and a process which combines thermal and catalytic treatment of heavy petroleum liquid in a slurry phase counterflow reactor, where liquid feed is fed from the top and hydrogen from the bottom.
2. Prior Art
Various designs have been utilized in the past for hydrotreatment of heavy petroleum oil in cocurrent mode in a slurry reactor. For example, FIG. 1 illustrates a typical conventional up-flow cocurrent slurry reactor. In this type of known reactor, a liquid petroleum feedstock and hydrogen are introduced to the bottom of a reactor vessel. The gaseous hydrocarbon product is removed from the top of the vessel after reaction.
Likewise, fixed bed catalyst systems for hydrotreatment of heavy petroleum crude are known. Fixed bed catalyst systems in the past have had two difficulties. The catalyst bed may get flooded and heavy oil tends to plug the bed.
There have also been a number of attempts at countercurrent reactor technology to treat lighter petroleum feed. U.S. Pat. No. 3,147,210 to Hass et. al. entitled TWO STAGE HYDROGENATION PROCESS illustrates a combination of cocurrent and countercurrent hydro processing of lighter hydrocarbons in a fixed bed catalyst system. An initial feedstock is subjected to catalytic hydrofining in cocurrent flow and then subjected to catalytic hydrogenation over a noble metal catalyst in countercurrent flow with hydrogen.
U.S. Pat. No. 5,939,031 to Ellis et. al. entitled COUNTERCURRENT REACTOR describes a countercurrent reactor design in a fixed bed catalytic hydroprocessing system. A bypass system is provided to overcome the problem of flooding the catalyst bed. The design illustrates a combination of a fixed bed reactor along with elements of a slurry reactor. Neither of the above-mentioned designs are suitable for heavy resid.
A countercurrent reactor has also been used to treat coal and oil sands as shown in Johanson et. al. U.S. Pat. No. 4,510,037 entitled HYDROGENATION PROCESS FOR SOLID CARBONACEOUS FEED MATERIALS.
There remains a need to provide a slurry phase reactor which will overcome the problems inherent with fixed bed catalyst reactors and cocurrent slurry phase reactors.
There is also a need to provide a process and apparatus for simultaneous and combined thermal and catalytic treatment of extra heavy crude oil.
There is a further need for a combined thermal and catalytic reactor having a hydrogen counter flow system.
There is a further need to provide a combined thermal and catalytic reactor wherein the heat required in the thermal phase zone is obtained from heat of reaction in the catalyst zone.
There is a further need to provide a reactor having a gas-phase thermal reaction zone, a liquid thermal reaction zone and a catalytic reaction zone which are integral within a single reactor vessel.
The present invention provides for combined thermal and catalytic treatment of heavy petroleum in a slurry phase counterflow reactor. The reactor system includes a reactor vessel which is typically vertically oriented and has three discrete regions.
Liquid feedstock, such as extra heavy petroleum crude oil, is brought to the reactor vessel through a feedstock inlet line which is in communication with the top of the reactor vessel in a gas phase thermal reaction zone. The liquid feedstock may be introduced via a nozzle into the reactor vessel below the level of a porous metal filter screen. The gas phase thermal reaction zone provides sufficient heat to the incoming feed to reach the reaction temperature so that thermal decomposition occurs. Lighter product is carried over by hydrogen through an outlet at the top.
Below the gas phase zone and in communication therewith is a liquid phase thermal reaction zone within the reactor vessel. Feedstock in liquid form from the gas phase thermal reaction zone passes by gravity to the liquid phase thermal reaction zone. To assist and encourage mixing within the liquid phase zone with upflowing hydrogen, a plurality of baffles extend from the interior wall of the reactor vessel and extend radially inward toward the axis of the vessel. In this zone, further thermal cracking takes place.
Heavier liquid within the liquid phase thermal reaction zone passes to a catalytic reaction zone below the liquid phase thermal reaction zone. Hot hydrogen gas is introduced and injected into the reactor vessel at the catalytic reaction zone through a hydrogen gas inlet. The hot hydrogen gas bubbles upward through the reactor vessel in countercurrent mode to the downward movement of the liquid feedstock. The hydrogen gas also assists in carrying the gaseous hydrocarbon product which is formed from the thermal and the catalytic treatment occurring within the reactor vessel.
Unconverted heavy residue along with solids (catalysts, metals and coke formed) are withdrawn from the bottom of the reactor.
The hydrogen gas and the gaseous hydrocarbon product move upward within the reactor vessel and are removed from the reactor vessel by a product outlet line in fluid communication with the top of the vessel. The hydrogen gas and gaseous hydrocarbon product are thereafter allowed to cool whereby the hydrocarbon product condenses to a liquid. At least a portion of the hydrogen gas is recycled through a hydrogen gas return line back to the hydrogen gas inlet.
The catalytic reaction zone will contain the desired amount and quantity of catalysts to chemically hydrogenate the liquid. Catalysts may be added or removed without shutting down of the process through a catalyst addition system. A portion of the residual stream exiting the outlet line at the bottom of the reactor may be directed through a buffer tank having a catalyst addition system. Accordingly, the amount of catalyst may be varied and controlled. Finally, the unconverted residual material having passed through the buffer tank returns to the catalytic reaction zone of the reactor vessel via a return line. This provides an additional advantage for further hydrogenation of unconverted residue.